Energy expenditure and aging: Effects of physical activity

Aging is associated with a decline in daily energy expenditure that is disproportionately greater than the decline in daily energy intake. Collectively, these events can create a "positive" energy balance, secondary gains in central and total body fat, and a subsequently higher risk of morbidity and mortality. Participation in regular physical activity is a logical strategy to attenuate the decline in energy expenditure with aging, as physical activity can comprise between 10-50% of an older person's daily energy expenditure. Understanding the influence of regular physical activity on energy expenditure with advancing age is clinically relevant, particularly since estimates predict that nearly 25% of the population will be greater than or equal to65 years of age by the year 2030. This brief review will focus on the current state of aging, energy expenditure, and physical activity literature. Topics to be addressed include: (a) measurement of physical activity in older adults; (b) aging and physical inactivity; and (c) influence of regular aerobic exercise on resting metabolic rate (RMR), thermic effect of food (TEF), and non-exercising physical activity.